The invention is directed to a method of separating blood into its components via a centrifuge system. One such centrifuge system includes at least one sampling device for blood, such as a needle, an inlet line connected between the sampling device and a centrifuge, a blood pump connected to the inlet line, a discharge line connected between the centrifuge and a receiving container, a first pump connected to the discharge line, and a discharge line system connected to the sampling device for recycling the blood components. Such a centrifuge system is known, for example, from DE-OS 39 31 471 (Apr. 11, 1991).
Blood centrifuges or plasmaphoresis devices are known, for example, from DE-OS 26 12 988 or its counterpart U.S. Pat. No. 4,113,173, in which the blood is taken into extracorporeal circulation with the aid of a needle, introduced to a centrifuge without the use of a rotary mechanical seal, separated there into its components and then returned to the patient through a second needle. This separation treatment is carried out essentially continuously, whereby the blood is separated in the centrifuge essentially into three main components, namely, the erythrocyte component (red blood cells), the buffy coat floating on the erythrocyte component (cell mixture, principally comprising thrombocytes (platelets) and leukocytes (white blood cells)), and the plasma component (which lies radially the farthest inward in the centrifuge due to its relatively low specific gravity). The degree of separation of the leukocyte and thrombocyte components may be up to about 70%; that is, at least 30% of the leukocytes introduced into the centrifuge are returned to the patient. However, this two-needle method is relatively unpleasant for the patient.
There is a plasmaphoresis device in the form of a centrifuge in which the separation is carried out with only one needle. Such methods have been described, for example, in DE-OS 27 45 041 or its counterpart U.S. Pat. No. 4,086,924, U.S. Pat. No. 4,531,932 (Jul. 30, 1985), DE-OS 39 31 471, EP-A-450,737 (Oct. 9, 1991) and EP-A-487,096 (May 27, 1992). However, the single-needle method must be carried out intermittently; that is, in a first cycle step, blood must be taken from the patient and introduced to the centrifuge and, in a second cycle step, the blood components are then returned to the patient. Although this method normally takes longer than a two-needle separation, it is desirable or even necessary in case the veins are cartilaginous or hard to find.
Moreover, the thrombocyte component is still contaminated with a certain portion of the lymphocytes, and the leukocyte component is contaminated with a portion of the erythrocytes and thrombocytes, so that a higher degree of purity is desirable. In order to improve the degree of separation and degree of purity, for example, DE-OS 39 31 471 proposes recirculation of certain separated blood components with untreated blood, but this brings about only a certain degree of improvement of the separating action.